# Protease Enzyme Supplementation in Weaning Piglets Fed Reduced Crude Protein Diets: Effects on Gut Health Integrity and Performance Response

## TL;DR

Adding protease enzymes to low-protein diets in weaning piglets can improve gut health and growth, reducing diarrhea risks.

## Contribution

The study demonstrates that protease supplementation in reduced-protein diets can support intestinal health and performance in weaned piglets.

## Key findings

- Protease-supplemented diets improved weight gain, feed intake, and reduced diarrhea in piglets.
- Protease improved amino acid digestibility but could not fully replace amino acid balancing in low-protein diets.
- Intestinal morphometry improved with protease supplementation, despite some inflammatory responses.

## Abstract

Weaning is a critical stage in pig production that challenges piglets’ health and growth due to abrupt dietary and environmental changes. These stressors often impair gut development, reduce enzyme production, and disrupt the intestinal microbiota, increasing the risk of diarrhea and poor performance. High-protein diets commonly used after weaning can worsen these effects, particularly due to anti-nutritional factors in soybean meals. Supplementing piglet diets with exogenous proteases has been proposed as a strategy to improve protein digestibility and gut health. In this study, we evaluated whether adding two commercial proteases to reduced-protein diets could alleviate post-weaning stress in piglets. We examined effects on intestinal integrity, inflammation, diarrhea incidence, and growth, as well as nutrient digestibility. Our findings contribute to understanding how dietary enzyme supplementation may support healthier and more efficient swine production during this vulnerable phase.

Two trials evaluated the effects of dietary protease inclusion in weaned piglets fed diets with or without crude protein (CP) reduction, focusing on performance, intestinal health, and amino acid digestibility. In Trial I, 270 piglets (21–63 days) received six treatments: control (PC), PC with 100 g/ton protease A (PC+A), CP reduced by 1.0% (NC1) or 1.5% (NC1.5), NC1.5 with 50 g/ton protease A (NC1.5+A), and NC1.5 with 50 g/ton protease B (NC1.5+B). PC+A improved weight gain, feed intake, and feed conversion compared with NC1.5+A. The incidence of diarrhea was reduced in animals fed protease-supplemented diets (PC+A, NC1.5+A and NC1.5+B). PC had greater ileal villus height than NC1.5+B, and PC+A showed a higher jejunal villus-to-crypt ratio than reduced CP groups. NC1.5+B increased jejunal expression of IL-6, TNF-α, and haptoglobin. In Trial II, 12 ileal-cannulated piglets received diets with or without protease A. Protease improved the standardized ileal digestibility (SID) of methionine+cysteine and tryptophan but reduced the SID of glycine and proline. While protease supplementation can improve some amino acids (Met+Cys and Thr) protein digestibility, our findings suggest it cannot fully replace careful amino acid balancing in CP-reduced diets. However, protease-supplemented diets were associated with improved intestinal morphometry and a reduced incidence of diarrhea.